In the packaging of goods in containers, such as corrugated cartons or the like, it is common practice to use a tape sealing machine with a tape applicator to apply a strip of sealing tape along one end, across the top (or bottom) generally formed by a pair of opposed flaps and along another end of such a container. The adhesive tape is usually of Bi-axially Oriented Poly-Propylene (BOPP) film with an adhesive layer on one side and a release coating on the other side for ease of unwind. To properly seal the flaps of the carton in order to provide sufficient holding force to the carton, The adhesive tape normally applied first to the one end which in most machines forms a vertical surface, from this vertical surface of the carton, across the horizontal surface formed by the pair of opposed flaps to the other end of the carton which normally is a second vertical surface so the shoulders or the corners of the carton formed at the intersections of the vertical and horizontal surfaces are tightly wrapped. The vertical portions of the tape on each of the ends or the carton are each referred to as a tape tab. The length of the tab is preset by the tape applicator to provide a desirable amount of adhesive holding force to the carton. The tab length is usually preset from 2″ to 2.5″, excessive tab length is costly and un-effective, inadequate tab length reduces the adhesive area and holding force to the carton and causes a defective package.
The tape applicator automatically applies and cut off the tape to seal each carton as the carton advances passed the tape applicator usually by being carried on a conveyor of the packaging machine. The tape is supplied from a tape roll mounted on the packaging machine frame or usually mounted on the frame of the applicator which forms part of the machine.
As is well known a proper tape application system involves the source of tape, tape delivery; tape applying, tape cutting, and tape wipe down.
Most major problems encountered in carton taping using a conventional tape applicator are related to the tape tension as follows:                (1) Low tension:                    Results in loose and wrinkled tape on carton; tape not cutting properly; extended tape tabs                        (2) High tension:                    Results in the tape being over-stretched and elongated causing the tape to shrink and pull back; premature tape cutting; tape flagging; tape snap back and crumple; shortened tape tab lengths                        
There are two manual tension adjustments in a conventional tape applicator, namely (1) mandrel tension control, (2) clutch roller tension control which can partially address the abovementioned tension related issues and the variable unwinding (peel-off) force from the tape dues to different adhesive formula (hot melt, acrylic or rubber); release coating; width of tape (2″ or 3″); application temperature; etc. A third tension adjustment (3) may be provided by an added-on attachment in the form of a nip roller mounted at the free end of a dancer arm and biased against the periphery of the tape roll,                (1) Tape Mandrel Tension Adjustment:                    The mandrel tension adjustment normally consists of a hub to hold the hub of the tape roll, rotatable on a shaft with friction washers, compression spring and adjusting knob as a mean to provide a rotational drag on the tape roll as the tape being dispensed. It is the first stage of tape tension control and is applied at the source of tape supply, and functions to prevent the tape roll from free spinning; over-spinning or tape over-stretching. The amount of tension adjustment is also based on the unwinding force required for the tape being used, for example: low tension setting for sticky or wider tape, higher tension setting for narrower width and tape with a release coating.            In carton sealing, the carton are being deliver in space sequence one by one, requiring the tape to be pulled from the tape roll intermediately. The tape roll rotation starts and stops at every taping cycle, it tends to over-spin every stop cycle after tape cutting. Over-spin of tape roll creates loose tape, which affects the tape cutting (tape un-cut or cut with extended tab length) as well as taping consistence in the following taping cycle.            More rotational drag is required to reduce the over-spinning, particularly when tape is being drawn from a new roll of tape with a large diameter (15″) due to the additional mass and inertia.            If the drag applied at the tape mandrel is too high it will normally lead to tape breakage; stretched and elongated tape; premature tape cutting; tab crumpling and/or shortened tabs.                        (2) Clutch Roller Tension Adjustment:                    Generally the tension adjustment mechanism used in the clutch roll is similar to the mandrel tension adjustment mechanism using a compression spring; friction washers and an adjusting knob to adjust rotational drag. The clutch roller also is provided with a one-way clutch bearing to permit the tape to advance toward an applicator roll that applies the leading end of the tape to the carton while preventing the tape travel in reverse direction i.e. back toward the tape roll. The clutch roller's surface is knurled to release the adhesion of the tape.            The tension control at the tape roll mandrel is in essence the farthest from the point of application of the tape to the carton and provides a first stage of tension control applied to the tape. The clutch roller is the second stage of tape tension control of the tape and is positioned on the tape path from the tape roll to the applicator roll at an intermediate location between the tape roll and applicator roll. The clutch roller provides a secondary tension control to supplement the tension adjustment of the tape roll mandrel. Its position is closer to the point of application and tape cutting, its tension adjustment affects proper tape cutting, taping quality and tends to stabilize the tape for the tape application cycle.            Similar to the tape roll mandrel adjustment, low tension setting on the clutch roller leads to loosely adhered wrinkled tape on the carton; tape not being properly cut or tape an extended tab length. High tension setting leads to stretched tape on the carton which shrinks and causes the tabs to pull backwards; tape breakage; tape cut prematurely; tape crumple; and/or the tape to snap away from the application roller; and/or generate a shortened length tab.                        (3) A nip roller dancer arm        A nip roller at the free end of a dancer arm tends to stabilize the tape tension at the tape source. The dancer arm is spring bias to [press the nip roller against the circumference of the tape roll, the nip roller governs the position of tape being peeled off from the tape roll. The round surface of the roller supports the tape as it peels off the tape roll as the tape roll unwinds and provides a smoother tape release thereby to minimize jerky movement of the tape which may cause tape breakages.        It is believed that all tape applicators on the market are equipped with the above mentioned two manual tension adjustments and some may also include the nip roller dancer arm. Generally the tape tension is adjusted to a desirable level based the type of tape being used before startup of the machine in order to provide a reliable tape closure. However, it is well known that the tape's tension changes as the tape is being applied. Specifically, the tape tension increases gradually as the tape roll is depleted from a new roll (Max. 15″ diameter) down to a smaller roll (Min. 3.3″ diameter) during the tape sealing operation. The increased tape tension leads to tape breakages, tape shrinkage, premature tape cut, tape not being applied due to snap back or shortened tab length etc. creating batches of defective packaged cartons. All these problems appear mostly after the tape roll has been depleted down to approximately 4″ to 5″ diameter. To avoid these problems, there are three common practices in the industry (1) Monitor the tape roll, re-adjust the tension control manually once or twice based on the remaining size of the tape roll. (2) Install a new tape roll and discard the remaining tape roll before the tape is fully depleted. (3) Use an over-graded thicker tape which can sustain a higher tension, allow an over-extended tab length in the initial low tension setting for new roll to compensate the increases of tape tension which shortens the tab length as the tape is depleting. (This approach resolved some of the problem but it also leads to the problem of cutting a thicker tape with low tension). All three approaches are not ideally effective and generally result in added production down time, waste of tape and increase cost of tape, etc.        The currently available tension controls and the add-on nip roller dancer arm in a conventional tape applicator can only be preset to accommodate a constant condition such as tape peel-off unwind force and resistance through the tape path etc., they are not sufficient to control the changing tape tension as occurs during the taping operation i.e. as the tape is being dispense and the diameter of the tape roll changes when the tape roll goes from a large roll to a smaller roll. The changes of tension originate mainly from the drag preset at the tape mandrel.        A simple example illustrates how the changes of tape roll size affect the changes of tape tension: A new roll of tape with a 15″ diameter dispenses 24″ long tape on a 20″ long carton rotates ½ revolutions to complete one taping cycle. On the other hand when the tape roll has depleted gradually down to a 3.5″ diameter tape roll, it must now rotate 2 revolutions to dispense the same 24″ long tape for the same 20″ long carton. The tape tension increase significantly dispensing the same length of tape from the smaller roll since it has to overcome the additional rotations with the rotational drag initially preset to rotate for ½ revolutions.        
Tape applicators as generally used to apply tapes to seal a carton operate by providing a leading tape which is wiped onto the leading face of a carton or case being sealed and secured thereto and then is applied over the adjacent edge of the case and along the top (or bottom of the case. The length of tape applied to the leading face of the case or carton i.e. extending from the adjacent edge to the adjacent end of the tape is normally referred to as the tab and the length of this tab in conventional machines changes significantly unless in the case of conventional machines the tape tension is adjusted as the diameter of the tape roll from which the tape is being drawn changes. Tension adjustment systems of the prior art as described above are not done on the fly and in any event do not generally provide adequate control to maintain the tab length reasonably constant as the diameter of the tape roll changes. The present invention provides a mechanism that maintains the tab length about the same length as the diameter of the tape roll changes.
The convention tape applicators as above indicated generally direct tape from the tape roll to an entry roll from which the tape passes onto a one way clutch roll and from there to a front applicator roll that applies the leading end of the case being sealed. It is known to provide a dancer arm with a nip roll at its free end and to lead the tape over the nip roll which is pressed against the periphery of the tape roll and facilitate peeling of the tape off the tape roll; see for example U.S. Pat. No. 4,592,188 issued Jun. 3, 1986 to Marchetti.
It is also known to provide slack in the tape between the clutch roll and the tape roll by replacing a fixed entry roll as commonly used with an entry roll that is mounted on the free end of a dancer arm that reciprocates the entry roll between a position adjacent to and a second position spaced farther from the clutch roll at the appropriate time in the taping cycle to generate slack in the tape between the tape roll and the clutch roll; see U.S. Pat. No. 8,327,902 issued Dec. 12, 2012 to Lam.
U.S. Pat. No. 8,176,959 issued May 15, 2012 to Lam teaches a multi-purpose machine that may be converted to apply tape as a conventional C-clip where the tape extends generally up one side of a case across the top (or bottom) and the down the side of the case opposite the one side or an L-clip where the tape extends up one side around a corner at the top (or bottom) of the case and then part way along the top (or bottom) of the case. The patent shows the clutch roll and inlet roll both mounted in fixed relationship on a dancer arm to accommodate movement of the front applicator arm and roll to an over travel position when L-clips are to be applied.